Shrinkproofing of wool with chromium complexes



United States Patent 2,890,926 SHRJNKPROOFING 0F WOOL WITH CHROMIUM COMPLEXES Clay E. Pardo, Jr., Albany, and Willie Fong, Richmond,

Califl, assignors to the United States of America as represented by the Secretary of Agriculture No Drawing. Application April 17, 1956 Serial No. 578,849 9 Claims. (01. 8-128) (Granted under Title 35, US. Code (1952), sec. 266) A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to processes for shrinkproofing and feltproofing protein textile fibers, particularly wool. In particular, the invention is concerned with procedures wherein the fibers are conditioned with an alkaline material and is then treated with a chromium complex of a carboxylic acid whereby to produce a fiber which exhibits a marked resistance to shrinkage as compared with the original fiber. Further objects and advantages of the invention will be obvious from the description herein.

It is well known that laundering causes severe shrinkage of woolen textiles. This technical disadvantage seriously restricts the application of wool in the textile industry and much research has been undertaken to modify the natural fiber to improve its shrinkage properties. In general, known methods of treating wool to improve its shrinkage properties have the disadvantage that the hand of the wool is impaired. This is particulanly true where resins. are applied to the textile.

It has now been found that if wool is treated with a chromium complex of a carboxylic acid, the shrinkage characteristics of the Wool are improved. It has further been found that if the wool is conditioned with an alkaline agent prior to treatment with the chromium complex, superior results are attained. The benefits of the alkaline pretreatment are explained as follows: When the alkaline pretreatment is used, the chromium complex can be applied in the form of a dilute solution, for example, a one percent solution, and the treated wool will exhibit a marked reduction in shrinkage properties. On the other hand if the alkaline pretreatment is not employed, one must use a chromium complex solution of considerably higher concentration to get the same degree of shrinkage protection. This significant difierence is demonstrated in Example I, below. Another point is that in many cases, the alkaline pretreatment yields a degree of shrinkage protection over and above that which would be expected from the amount of chromium complex taken up by the wool. This important advantage of the alkaline pretreatment is also demonstrated in Example I, below.

The reason for the eifectiveness of the alkaline conditioning or pretreatment step is not known for certain.

It is believed however that when the Wool is treated with the alkaline agent it assumes a net negative charge thus increasing the attraction between it and the positively charged cationic chromium complex. Also, when the wool is conditioned with the alkaline material, hydroxyl groups are adsorbed by the wool molecules, which to a certain extent exhibit ion adsorbing properties. These adsorbed hydroxyl ions then act as sites which attract the cations of the chromium complex. As a result, the chromium complex is more firmly bonded to the wool molecules than Where the wool has not been pretreated with the alkaline agent. It may be, however, that other mechanisms are responsible for the elfect of the conditioning step and we do not intend to limit the invention to any theoretical basis. The important point is that the conditioning step has been demonstrated to provide improved results on shrinkage protection When it is used in connection with a chromium complex.

In applying the process of this invention, the wool is conditioned with an alkaline agent, that. is, the wool is impregnated with an aqueous solution of an alkaline agent. The treatment is advantageously performed by immersing the wool in an excess of the alkaline solution or by applying the solution by spraying or other conventional application techniques. To assist in wetting the wool with the solution, it may be run through padding rolls or the like. Various alkaline materials may be used, as for example, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, borax, potassium borate, ammonium hydroxide, trisodium phosphate, disodium hydrogen phosphate, sodium citrate, sodium pyrophosphate, or other alkali metal salts which yield alkaline solutions. One may also use salts of alkali metals with organic carboxylic acids, such as sodium oxalate, which do not form alkaline solutions but which have acid-neutralizing capacity and hence can be considered as alkaline agents within the scope of this invention. The concentration of the alkaline agent may be varied, depending on several factors for example, the alkalinity of the agent in question, the degree of shrinkproofing to be obtained, and the nature and concentration of the chromium complex used in the succeeding operation. With regard to the later item, the chromium complex is generally of an acid nature and higher concentrations of the chromium complex require application of a higher concentration of alkaline material. Taking into account these factors, the concentration of the alkaline agent may be as low as about 0.01 molar or as high as about 1 molar. Usually, the chromium complex is applied as a 1% solution and in such case the concentration of the alkaline agent is preferably in the range from about 0.02 to about 0.2 molar.

In the next step the wool wet with the alkaline solution is immersed in a solution of the chromium complex. To assist in wetting the wool with the solution, it may be run through padding rolls or the like. The chromium complex is generally applied as an aqueous solution of about 1 to 10% concentration, preferably about 0.5 to 2%, and, if desired, the solvent may be a volatile polar solvent such as ethanol, methanol, propanol, isopropanol, acetone, etc. The solvent may also be mixtures of water and such organic solvents.

The wool which has been subjected to the chromium complex is then dried. Generally, the drying is accomplished by subjecting the wet wool to a current of air heated, for example, to a temperature of 50 to C. The drying fixes the chromium complex to the Wool so that it is rendered insoluble and cannot be removed by washing.

For the purposes of this invention we may use any of the chromium complexes of carboxylic acids. The preparation of these compounds, as well known in the art, involves reaction of the carboxylic acid with chromic chloride or chromyl chloride, usually in the presence of ethanol or other low-molecular Weight alkanol. The carboxylic acid may be of the aliphatic, aromatic, or cycloaliphatic types. Typical examples are acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, heptoic acid, caprylic acid, nonylic acid, capric acid, undecylic acid, lauric acid, myristic acid, palm-itic acid, stearic acid,

benzoic acid, toluic acid, hexa hydrobenzoic acid, cyclo hexane-carboylic acid, cyclohexane-acetic acid, and so forth. Generally, it is preferred to employ the chromium complexes of carboylic acids which contain 4 or more carbon atoms. The chromium complexes can also be derived from carboxylic acids wherein some or all of the hydrogen atoms attached directly to carbon are replaced by fluorine atoms. are, for example:

Heptafluoro-butyric acid, Nonafluoro-valeric acid, Undecafiuoro-caproic acid, Pentadecafluoro-caprylic acid, Nonadecafiuoro-capric acid, Tricosafluoro-lauric acid,

Heptacosafluoro-myristic acid, Perfluoropalmitic acid (C F COOH), Perfluorostearic acid (C17F35COOI'I), Undecafluorocyclohexane carboxylic acid, Tridecafluoro-cyclohexane acetic acid, and so forth.

Chromium complexes of carboxylic acids which may be used in accordance with this invention are disclosed by Reid, U.S. Patent 2,662,835; Iler, U.S. Patent 2,273,040; and Iler, Ind. and Eng. Chem., vol. 46, pp. 766-769.

The procedure of this invention is particularly adapted for treatment of wool but may also be applied to other proteinous fibers such as mohair, fibers from other fleecebearing animals, animal hair, silk, fibers made from proteins such as zein, casein, peanut protein, keratin, etc. The proteinous fiber may be in the form of actual fibers or may be in the form of threads, yarns, woven or knitted material, garments, etc.

The invention is further demonstrated by the following examples which are given merely by way of illustration and not limitation. Procedures which are not within the scope of the invention are included in the examples for comparison purposes.

EXAMPLE I Woolen cloth was extracted successively with ether, alcohol, and water to remove extraneous materials. Two Z-gram samples of the extracted woolen cloth were immersed in a 100 ml. bath of aqueous sodium borate, the concentration of the latter being 0.05 molar. The cloth was run through padding rolls to assist in wetting it with the borax solution. The cloth samples which had picked up about 120 to 150% of their weight of solution were then immersed in 50 ml. of a 1%. aqueous solution of a chromium complex and allowed to soak therein for 20 minutes. The cloth samples were then removed from this solution and dried in an oven for one hour at 50 C.

Two Z-gram samples of the extracted woolen cloth were treated with the 1% solution of the chromium complex, as described, but omitting the pretreatment with the sodium borate treatment.

Two 2-gram samples of the extracted woolen cloth were treated with a 3% solution of the chromium complex in the manner described but omitting the pretreatment with the sodium borate solution.

The chromium complex used in these experiments was a product prepared by reacting chromyl chloride, in the presence of an alcohol, with a saturated perfluoro-monocarboxylic acid having 4 to 10 carbon atoms in the mole cule. This preparation is sold by the Minnesota Mining & Manufacturing Co. under the name EC-804 and its production is described in U.S. Patent No. 2,662,835.

The dried cloth samples were weighed to determine the uptake of chromium complex ineach difierent treatment. The shrinkage characteristics of the cloth samples was determined by subjecting them to a laundering operation in which the samples were violently agitated in 0.5% solution of sodium oleate at 40 C. with a cloth to solution ratio of 1:50, the area of the cloth being measured before and after laundering. With this method of laundering, untreated cloth samples gave area shrinkages 01546 to 50%.

The results obtained are set forthbelow. In every case, the results are the average of each duplicate run.

Typical acids of this type Table 1 Concentration Uptake of Conditionof chromium chromium Area Expt. ing agent complex in complex shrinkage,

treating $01., by cloth, percent percent percent 1 sod. borate" 1 3.8 9. 5 2 none .1 1 2.13 30. 2 3 none 3 3. 72 19. 9

EXAMPLE II A series of experiments were carried out using the 'following technique in each instance:

Two 2-gram samples of woolen cloth (extracted as described in Example I) were immersed in a ml. bath of an aqueous alkaline medium, the alkaline agent and concentration being specified below. The cloth was run through padding rolls to assist in wetting it with the solution. The cloth samples which had picked up about to of their weight of solution were then immersed in 50 ml. of a 1% solution of the same chromium complex as used in Example I. The cloth was allowed to stand in this solution for 20 minutes then removed and dried in an oven for 1 hour at 50 C. In one of the experiments (control) no alkaline conditioning nor treatment with the chromium complex was employed.

The dried cloth samples were tested for shrinkage as described above in Example I. The results obtained are set forth below. In every case the results are the average of each duplicate run.

Table II Uptake of Area Expt. Conditioning agent and conchromium shrinkage,

centration complex, percent percent Sodium hydroxide, 0.1 M 7. 6 l1. 6 Sodium carbonate, 0.05 M 3. 4 12. 9 NEzHPO4, 0.05 M 5. 1 15. 2 Sodium citrate, 0 033 M 4. 6 11.2 Sodium oxalate, 0 05 M 4. 8 13.0 (Control) none none 46. 7

EXAMPLE III A series of experiments were carried out as described in Example 11. In this instance the alkaline agent in the conditioning step was sodium borate (borax) applied at various concentrations. The chromium complex was the same as in Example I.

In a control experiment (No. 4), the wool was subjected to the alkaline conditioning but was not treated 8 1th the chromium complex. The results are tabulated e ow.

Table IV Molar coneen- Uptake of Area Expt. tration of chromium shrinkage,

sodium bycomplex, percent droxide percent 2. 9 l5. 2 4. 5 11. 4 7. 3 16. 1 0.25 7. 1 16. 6 none used 2. 8 22. 3

EXAMPLE V A series of experiments was carried out using the following technique in each instance.

Two 2*gram samples of (non-extracted) woolen cloth were immersed in a 100 ml. bath of an aqueous solution of sodium borate of 0.05 molar concentration. The cloth was run through padding rolls to assist in Wetting it with the solution. The wet cloth samples were then immersed in 5 ml. of an aqueous solution of a complex of chromic chloride and stearic acid. (Various concentrations of this agent were used as specified below.) The cloth was allowed to remain in the solution 30 minutes then removed and dried in an oven at 100 C.

In a control run, samples of the cloth were treated with the borax solution but were not treated with the chromium complex.

The treated samples were tested as described above; the results are tabulated below:

Having thus described the invention, we claim:

1. A process for shrinkproofing wool which comprises impregnating the wool with an aqueous solution of an alkaline agent having a concentration of about from 0.01

to 1 molar, said alkaline agent being selected from the group consisting of ammonium hydroxide, alkali metal hydroxides, alkali metal salts which yield alkaline solu tions, and alkali metal salts which have acid-neutralizing capacity, and treating the impregnated wool V with a 10 chromium complex of a carboxylic acid selected fromthe group consisting of alkanoic acids, benzene acid, toluic acid, cyclohexane-carboxylic acid, cyclohexane-acetic acid, fluorinated alkanoic acids, fluoriiiated cyclohexane carboxylic acid, and fluorinated cyclohexane-acetic acid.

2. The process of claim 1 wherein the alkaline agent is sodium borate. v

3. The process of claim 1 wherein the alkaline agent is sodium hydroxide.

4. The process of claim 1 wherein the alkaline agent is sodium carbonate.

5. The process of claim 1 wherein the alkaline agent is sodium phosphate.

6. The process of claim 1 wherein the alkaline agent is sodium citrate.

7. The process of claim 1 wherein the chromium complex is a complex of chromic chloride and an unsubstituted, aliphatic carboxylic acid.

8. The process of claim 1 wherein the chromium complex is a complex of chromic chloride and stearic acid.

9. The process of claim 1 wherein the chromium complex is a complex of chromyl chloride and a perfluoroaliphatie carboxylic acid.

References Cited in the file of this patent OTHER REFERENCES Moncrieif: Wool Shrinkage, Natl Trade Press Ltd., London, 1953, pp. 366-369.

McLaughlin et al.: The Chem. of Leather Manufi, Reinhold Pub. Co., N.Y., 1945, pp. 4234.

Textile Colorist, August 1942, pp. 406 and 410.

Alexander: Amer. Dyestutf Reporter, June 26, 1950, 

1. A PROCESS FOR SHRINKPROOFING WOOL WHICH COMPRISES IMPREGNATING THE WOOL WITH AN AQUEOUS SOLUTION OF AN ALKALINE AGENT HAVING A CONCENTRATION OF ABOUT FROM 0.01 TO 1 MOLAR, SAID ALKALINE AGENT BEING SELECTED FROM THE GROUP CONSISTING OF AMMONIUM HYDROXIDE, ALKALI METAL HYDROXIDES, ALKALI METAL SALTS WHICH YIELD ALKALINE SOLUTIONS, AND ALKALI METAL SALTS WHICH HAVE ACID-NEUTRALIZING CAPACITY, AND TREATING THE IMPREGNATED WOOL WITH A CHROMIUM COMPLEX OF A CARBOXYLIC ACID SELECTED FROM THE GROUP CONSISTING OF ALKANOIC ACIDS, BENZOIC ACID, TOLUIC ACID, CYCLOHEXANE-CARBOXYLIC ACID, CYCLOHEXANE-ACETIC ACID, FLUORINATED ALKANOIC ACIDS, FLUORINATED CYCLOHEXANECARBOXYLIC ACID, AN FLUORINATED CYCLOHEXANE-ACETIC ACID. 